Circular 29/2022/TT-BCT Technical safety standards for explosion-proof leakage current relays up to 1140V used in underground mines

 

 

NATIONAL TECHNICAL REGULATION ON SAFETY FOR RELAYS PROTECTING ELECTRICAL LEAKAGE CURRENTS VOLTAGE UP TO 1 140 V EXPLOSION-PROOF USED IN UNDERGROUND MINES

hereinafter referred to as explosion-proof leakage current protective relay

 

This technical regulation sets out technical requirements, testing methods, sampling procedures; management requirements; responsibilities of organizations and individuals producing, trading, and importing cigarettes.

Thông tư này quy định chi tiết khoản 4 Điều 38 Luật Thủy sản số 18/2017/QH14 đã được sửa đổi, bổ sung tại điểm c khoản 21 Điều 14 Luật số 146/2025/QH15.

This technical regulation specifies technical safety requirements and management for relays protecting electrical leakage currents voltage up to 1 140 V explosion-proof in three-phase isolated neutral AC power networks used in underground mines with flammable gases and explosive dust (hereinafter referred to as explosion-proof leakage current protection relays), having HS code 8535.90.90.), with HS code 8535.90.90.Locking resistance

Thông tư này áp dụng đối với tổ chức, cá nhân có liên quan đến hoạt động kinh doanh đối tượng thủy sản nuôi chủ lực trên lãnh thổ Việt Nam.

This technical regulation applies to organizations and individuals producing, importing, testing, inspecting, certifying, appraising using and other individuals related to explosion-proof leakage current protection relays in underground mines within the territory of Vietnam.

In this technical regulation, the following terms are understood as follows:

3.1. Explosive atmosphere is a mixture of flammable substances in the form of gas, vapor, dust, fiber, or flying particles with air, in which conditions allow flame to spread continuously.

3.2. Leakage current protection relay is a device that can automatically cut off the power supply to the load network when the leakage resistance value of the network equals or is less than the set value.

3.3. Lockout leakage current protection is a type of protection that does not allow power to be supplied to the load network when the leakage resistance of the network monitored decreases to the set value.

3.4Network leakage resistance is the total three-phase insulation resistance of the network to ground.

3.5. Leakage current is the current flowing between the live phase of the network and ground due to reduced insulation resistance.

3.6. Leakage current actuating resistance is the highest leakage resistance value that causes the leakage current protection device to act.

3.7limit Lockout leakage resistance

3.8. is the highest insulation resistance value of the load network that causes lockout leakage current protection to act. Network capacitance

3.9. is the total capacitance of the phases to ground. Self-check function

3.10. is a function that can automatically cut off power when the relay cannot operate normally due to its own failure or malfunction. Long-term leakage current

3.11. is the current flowing through the leakage resistance without causing the leakage current protection device to act when the insulation resistance is greater than the actuating resistance and the network capacitance within the operating range.ắis the steady-state current flowing through the leakage resistance equal to the minimum calculated body resistance when the insulation resistance is greater than the network impedance and capacitance within the operating range, appearing during the leakage protection interruption period until the motor stops. 5. Requirements

3.12. Non-sparking enclosure type "d"” is a structure containing parts that may ignite an explosive gas mixture and can withstand the pressure generated inside the explosion of the explosive gas mixture and prevent the spread of the explosion to the surrounding explosive atmosphere.

3.13. Non-incendive protection type "i"” is a type of protection where the electrical energy of the equipment and connected components, when placed in an explosive atmosphere, is limited below the level capable of igniting an explosive mixture by spark or thermal effects.

II. TECHNICAL SAFETY REQUIREMENTS

4. Referenced Documents

4.1. QCVN 01:2011/BCT National Technical Regulation on Safety in Coal Mine Extraction.

4.2. QCVN 04:2017/BCT National Technical Regulation on Safety in Metal Ore Mine Extraction.

4.3. TCVN 4255:2008 (IEC 60529:2001) Protection by Enclosures (IP Code).

4.4. TCVN 10888-0:2015 (IEC 60079-0:2011) Explosive Atmospheres - Part 0: Equipment - General Requirements.

4.5. TCVN 10888-1:2015 (IEC 60079-1:2014) Explosive Atmospheres - Part 1: Protection of Equipment by Non-sparking Enclosure Type "d".

4.6. TCVN 7079-7:2002 Electrical Equipment for Underground Mines - Part 7: Enhanced Safety - Type "e".

4.7. TCVN 7079-11:2002 Electrical Equipment for Underground Mines - Part 11: Non-incendive Protection - Type "i".

4.8. TCVN 7079-17:2003 Electrical Equipment for Underground Mines - Part 17: Inspection and Maintenance of Equipment.

4.9. IEC 60079-7:2015 Explosive Atmospheres - Part 7: Protection of Equipment by Enhanced Safety "e" (Explosive Atmospheres - Part 7: Protection of Equipment by Increased Safety "e"Average loan repayment period is 10 years;”).

).Explosive Atmospheres - Part 11: Protection of Equipment by Intrinsic Safety "i" ( Explosive Atmospheres - Part 11: Protection of Equipment by Non-incendive Protection "i").

).Explosive Atmospheres - Part 17: Electrical Installations Inspection and Maintenance ().

Figure 7. Threaded coupling for explosion-proof joints, screwầGeneral Requirements

5.1. The explosion-proof earth leakage relay used in underground mines must meet the technical safety requirements for ordinary earth leakage relays used in environments without flammable gases and explosive dust, as well as the requirements set forth in this Technical Regulation.

5.2. Classification of explosion-proof earth leakage relays

5.2.1. Classification according to product design and manufacture

5.2.1.1. Type designed for independent use in electrical networks;

5.2.1.2. Type designed in block form or integrated for use within explosion-proof electrical equipment.

5.2.2. Classification according to rated voltage

The rated alternating current voltage (U_{Average loan repayment period is 10 years;}) of the explosion-proof earth leakage protection device: 127 V, 220 V, 380 V, 660 V, and 1 140 V.

5.2.3. Classification according to network capacitance compensation

5.2.3.1. With network capacitance compensation;

5.2.3.2. Without network capacitance compensation.

5.3. Requirements for operating conditions

5.3.1. Rated frequency: 50 Hz.

5.3.2. Operating mode: Continuous.

5.3.3. Ambient temperature:

5.3.3.1. For type used independently in electrical networks: From -20 °C to +40 °C;

5.3.3.2. For type designed in block form or integrated for use within explosion-proof electrical equipment: Up to 60 °C.

5.3.4. Relative humidity value up to (98 ± 2) % at 35 °C.

5.3.5. Supply voltage fluctuation from 0.85 to 1.1 times the rated value;

5.3.6. Network capacitance change from 0 to 1.0 µF per phase;

5.3.7. In hazardous environments with flammable gases and explosive dust, the dust concentration does not exceed 1 200 mg/m³.

5.4. Requirements for installation location

5.4.1. Tilt angle not exceeding ±15 ° in all directions relative to the vertical axis and in chambers, stations, and tunnels with structures ensuring safety.

5.4.2. Dry and properly ventilated according to the provisions of Article 42 QCVN 01:2011/BCT for coal mines and Article 43 QCVN 04:2017/BCT for ore mines.

5.4.3. Free from the effects of corrosive vapors or gases that damage insulation.

5.4.4. Elevation not exceeding 1 000 m above sea level for types used independently in electrical networks.

5.5. Requirements for construction

5.5.1. Requirements for grounding parts

5.5.1.1. Grounding requirements must comply with the provisions of Clause 20 Article 102 QCVN 01:2011/BCT and Articles 5.1, 5.2, 5.4, and 5.5 TCVN 10888-0:2015 (IEC 60079-0:2011).

5.5.1.2. The position of the grounding wire connection must be red.

5.5.2. Explosion-proof earth leakage relays used in underground mines must have a mounting bracket on the lower part of the housing and upper hooks for ease of installation, movement, and operation.

5.5.3. The cover of the explosion-proof earth leakage relay must be mechanically interlocked to ensure:

5.5.3.1. It can only be opened when the switch is in the off position.

5.5.3.2. The switch cannot close when the cover is open.

5.6. When the earth leakage relay is in the off position or not working, it must automatically cut power to the load supply devices.

5.7. Test buttons, switch positions of the explosion-proof earth leakage relay must have non-erasable operation symbols.

6. Requirements for explosion-proof types of earth leakage relays

The explosion-proof types of earth leakage relays used in underground mines with flammable gases and explosive dust must be designed, manufactured, and tested in accordance with standards: TCVN 10888-0:2015 (IEC 60079-0:2011), TCVN 10888-1:2015 (IEC 60079-1:2014), TCVN 7079-7:2002, TCVN 7079-11:2002 corresponding to the explosion-proof types and the provisions of this Technical Regulation.

6.1. Main components of the "d" type non-explosive penetration-proof enclosure include:

6.1.1. Explosion-proof enclosure and cable junction box.

6.1.2. Cable entry connector and cable exit connector.

6.1.3. Porcelain penetrating through the enclosure wall and partition.

6.1.4. Light-transmitting element.

6.1.5. Control button, switch lock.

6.1.6. Mechanism for transmitting rotary or linear motion.

6.1.7. Locks, related holes, and empty elements.

6.1.8. Special clamping mechanism.

6.1.9. Interlocking mechanism.

6.1.10. Quick-opening lid.

6.2. Requirements for "d" type non-explosive enclosures

6.2.1. Types of explosion-proof joints

Explosion-proof joints must comply with the provisions of Articles 5, 6, 7, and 8 TCVN 10888-1:2015 (IEC 60079-1:2014) and the provisions of this Technical Regulation.

6.2.1.1. Explosion-proof joint in tube or cylindrical shape without bolt holes as shown in Figure 1.

Note:

of - Width of the explosion-proof joint surface, mm.

For coal-fired thermal power plants where the enterprise holds 100% of the registered capital and uses 100% of its own capital to invest in the project approved by the competent authority, E is determined as 100%; - Width of the explosion-proof joint cylindrical face, mm.

f - Clearance of the chamfered edge, mm.

L - Minimum width of the explosion-proof joint, mm; L = c + For coal-fired thermal power plants where the enterprise holds 100% of the registered capital and uses 100% of its own capital to invest in the project approved by the competent authority, E is determined as 100%; with the condition: of ≥ 3,0 mm, f ≤ 1,0 mm.

T - Inside of the equipment casing.

Figure 1. Explosion-proof joint in tube or cylindrical shape without bolt holes

6.2.1.2. Explosion-proof joint in tube or cylindrical shape with bolt holes as shown in Figure 2.

Note:

a - Width of the cylindrical flange, mm.

The Standing Office of the Council for International Cooperation on Non-Governmental Organizations (Vietnam Friendship Association) is the agency responsible for receiving registration dossiers, leading, and coordinating with member agencies of the Council to examine dossiers and return results of reviews of registration dossiers of foreign non-governmental organizations in Vietnam. - Width of the explosion-proof joint flat surface to the bolt hole, mm.

international - Clearance of the cylindrical joint, mm.

l - Minimum distance from inside the equipment to the bolt hole, mm; l = a + b if international ≤ 0,2 mm.

L - Minimum width of the explosion-proof joint, mm.

T - Inside of the equipment casing.

Figure 2. Explosion-proof joint in tube or cylindrical shape with bolt holesngenergy

6.2.1.3. Explosion-proof joint in flat flange shape as shown in Figure 3.

Note:

l - Minimum distance from inside the equipment to the bolt hole, mm.

L - Minimum width of the explosion-proof joint, mm.

T - Inside of the equipment casing.

Figure 3. Explosion-proof joint in flat flange shapePursuant to Decree No. 97/2016/NĐ-CP dated July 1, 2016 of the Government stipulating the contents of statistical indicators under the national statistical indicator system;energy

6.2.1.4. Minimum distance from inside the equipment to the bolt hole must comply with the provisions of Table 1.

Table 1. Minimum distance from inside the equipment to the bolt hole.of the Government stipulating functions, tasks, powers, and organizational structure of the Ministry of Home Affairs12,5 ≤ L< 25

- Gasket.

Note:

G Figure 4. Explosion-proof joint in flange shape with gasket

L - Minimum width of the explosion-proof joint, mm.

T - Inside of the equipment casing.

6.2.1.6. Explosion-proof joint in rotating shaft shape as shown in Figure 5.

L - Minimum width of the explosion-proof joint, mm.

Note:

If passing through the non-explosive enclosure wall is required, the width of the joint must comply with the provisions of Article 7 TCVN 10888-1:2015 (IEC 60079-1:2014).

Figure 5. Explosion-proof joint in rotating shaft shape

6.2.1.7. Explosion-proof joint in rotating shaft shape with bushing as shown in Figure 6.

Figure 6. Explosion-proof joint in rotating shaft shape with bushing

Note:

If passing through the non-explosive enclosure wall is required, the width of the joint must comply with the provisions of Article 7 TCVN 10888-1:2015 (IEC 60079-1:2014).

6.2.1.8. Explosion-proof joint in threaded screw type complying with Article 5.2.8 and Article 5.3 TCVN 10888-1:2015 (IEC 60079-1), as shown in Figure 7.No.- Thread pitch.

- Thread engagement length, mm.

Note:

d.1. Amount of taxable income in Vietnam: α

Y - Thread apex angle, degrees.

Figure 7. Explosion-proof joint in threaded screw type 6.2.2. Minimum width and clearance of the explosion-proof joint:

6.2.2. Width and minimum clearance of explosion-proof joint:

6.9.4. Any thermal effects generated in the locking leakage current spark-safe circuits must ensure that they do not cause ignition of gas mixtures due to surface heating according to Clause A.1 b) IEC 60079-11:2015.

6.2.2.1. For joint types such as pipe, cylindrical, flange, and rotating shaft: In accordance with the provisions of Table 2 of this Technical Standard.

Table 2. Minimum width and clearance of explosion-proof joints

6.2.2.2. For thread and bolted joints, the following requirements must be met:

6.2.2.2.1. At least five threads must engage each other.

6.2.2.2.2. Thread pitch ≥ 0.7 mm.

6.2.2.2.3. The apex angle of the thread teeth is 60° (± 5°).

6.2.2.2.4. The length of thread engagement ≥ 5 mm for V ≤ 100 cm³.

6.2.2.2.5. The length of thread engagement ≥ 8 mm for V > 100 cm³.

6.2.3. Special clamping devices

6.2.3.1. Clamping devices must comply with Article 9 of TCVN 10888-0:2015 (IEC 60079-0:2011).

6.2.3.2. For explosion-proof protection "d" type clamping devices, they must comply with the provisions of Clause 6.2.3.1 of this Technical Standard and Article 11 of TCVN 10888-1:2015 (IEC 60079-1:2014).

6.2.3.3. All explosion-proof joints using bolts must have anti-loosening washers and can only be opened with tools.

6.2.4. Quick-opening covers must have interlocking mechanisms; they can only be opened after power has been cut off and the interlocking mechanism has been released.

6.2.5. Cable entry ports

Cable entries to the cable junction box of the explosion-proof earth leakage relay must comply with the provisions of Article 16 and Appendix A of TCVN 10888-0:2015 (IEC 60079-0:2011), Article 13 of TCVN 10888-1:2015 (IEC 60079-1:2014), and the following requirements:6.2.5.1. Must be securely fastened to the enclosure and have all necessary parts to seal and clamp cables, including one of the types of cable glands shown in Figure 8.

- Rubber sealing ring.

Note:

1 - Rubber cable.

2 - Cable clamp detail.

3 - Detail for cable entry to compress rubber gasket.

4 - Enclosure.

5 - Outer diameter of rubber cable, mm

For coal-fired thermal power plants where the enterprise holds 100% of the registered capital and uses 100% of its own capital to invest in the project approved by the competent authority, E is determined as 100%; - Inner diameter of cable gland, mm.

D1 D2, D3

- Outer and inner diameters of rubber gasket, mm. Figure 8. Cable gland when assembled

6.2.5.2. The distance between the cable gland, gasket, and rubber cable must comply with the provisions of Table 3 of this Technical Standard. đTable 3. Distance between cable gland, gasketNo.international

and rubber cable

Distance fromn l6.2.5.3. The components of the cable gland must be tightened to ensure sealing performance. 6.2.5.4. The rubber gasket must ensure no cracking, good elasticity, and that the cable is not stretched or bent during assembly and operation.

6.2.6. Unconnected cable glands must be sealed as shown in Figure 9 or another similar sealing method.

- Sealing plug.

- Rubber sealing ring.

- Detail for cable entry and exit to seal.

Note:

1 Figure 9. Unconnected cable gland

2 6.3. Transparent elements

3 Transparent elements must comply with the provisions of Article 9 of TCVN 10888-1:2015 (IEC 60079-1:2014) and Article 26 of TCVN 10888-0:2015 (IEC 60079-0:2011).

4 - Detail for cable entry to compress rubber gasket.

6.4. Materials for the enclosure

6.4.1. Non-metallic materials

Non-metallic materials used to manufacture parts, components, and sections of the enclosure of the explosion-proof earth leakage relay must comply with the provisions of Article 7 of TCVN 10888-0:2015 (IEC 60079-0:2011).

6.4.2. Metallic materials

Metallic materials used to manufacture parts and sections of the enclosure of the explosion-proof earth leakage relay must comply with the provisions of Article 8 of TCVN 10888-0:2015 (IEC 60079-0).

6.5. Insulation bushings (porcelain inserts), terminal blocks passing through the walls of the enclosure must comply with the provisions of Article 11 of TCVN 10888-0:2015 (IEC 60079-0:2011) and must ensure no damage during electrical wire connections.

6.6. Connection means and cable junction boxes must comply with the provisions of Articles 14 and 15 of TCVN 10888-0:2015 (IEC 60079-0:2011).

6.7. The relative flashover index of insulating materials used in the explosion-proof earth leakage relay must comply with the provisions of Clause 4.4.1 of IEC 60079-7:2015, and the relative flashover index of solid insulating materials (CTI) must comply with the provisions of Table 4 of this Technical Standard.

Table 4. Relative flashover index of solid insulating materials

Material group

Relative flashover index (CTI)

CTI ≥ 600

Rated voltage U

Minimum creepage distance (mm)

Illa

- Operating voltage may exceed 10% of the voltage level listed in the table above.

6.9.4. Thermal effects generated in the safe ignition spark lockout circuits under any circumstances must ensure that the surface temperature does not ignite the gas mixture according to Clause A.1 b) of IEC 60079-11:2015.

6.9.5. Lockout circuits must be isolated from other safe ignition spark circuits and from non-safe ignition spark circuits according to Clause A.1 b) of IEC 60079-11:2015.

7. Technical requirements for explosion-proof earth leakage relays

7.1. Basic parameters of the explosion-proof earth leakage relay

6.9.5. The locking leakage current circuits must be isolated from other spark-safe circuits and from non-spark-safe circuits according to Clause A.1 b) IEC 60079-11:2015.

7. Technical requirements for explosion-proof leakage current protective relays

7.1. Basic parameters of explosion-proof leakage current protective relays

8.1.1. Ambient temperature from -20 °C to +40 °C;

The basic parameters of the earth leakage protection relay for explosion-proof and leakage lockout must comply with the provisions set out in Table 6 of this technical regulation.

Table 6. Values of earth leakage resistance, leakage lockout resistance, and operating timeinternationalType, Model

Industrial frequency test voltage value (Vac)

60 < U

300 < U

660 < Uần sNo. 800 < U

Insulation resistance values for different rated voltages must comply with the provisions set out in Table 9 of this technical regulation.

Table 9. Insulation resistance values Rated insulation voltage

7.3.3. The component for compensating the capacitive part of the leakage current must operate continuously and must comply with the requirements established in the technical specifications of the manufacturer for earth leakage protection relays.

7.3.4. The earth leakage protection relay for explosion-proof must operate;

Bn l7.3.4.1. Not more than 0.1 seconds and have the capability to disconnect the network when the voltage at the terminals drops to 0.6 times the rated voltage of the network.

7.3.6.1. Spark safety;

7.3.6.2. Use positive pole for grounding;

7.3.6.3. The DC voltage of the unidirectional cable source used to detect earth leakage of the network or reduction of insulation resistance to ground must not exceed 40 Vdc; the current used to detect earth leakage resistance or leakage lockout resistance of the network insulation to ground must not exceed 5 mA.

7.3.7. The earth leakage protection relay must have a self-check function to ensure that it does not allow energization when the relay is damaged.

7.3.8. The earth leakage protection relay and leakage lockout relay must have a function to check the operation of the leakage action and leakage lockout action by creating artificial leakage with a test resistance value equal to 80% of the setting value.

7.4. Structural requirements for earth leakage protection relays for explosion-proof

7.4.1. Earth leakage protection relays installed integrated in other explosion-proof equipment must be manufactured as a unit within enclosures with an IP 54 protection rating in accordance with TCVN 4255:2008 (IEC 60529:2001), the connectors must have non-interchangeable functions.

7.4.2. On the enclosure of independent earth leakage protection relays with non-explosive-proof enclosures of type "d" must have the following devices and mechanisms:

7.4.2.1. A meter indicating the insulation resistance of the power grid;

7.4.2.2. Adjustment device for capacitive compensation;

7.4.2.3. Color signal display for operational status and fault status:

7.4.2.3.1. Red - leakage,

7.4.2.3.2. Green - normal operation,

7.4.2.3.3. Yellow - leakage lockout;

7.4.2.4. Test button to simulate leakage and leakage lockout;

7.4.2.5. Grounding terminal for the leakage test circuit;

7.4.2.6. Switch-on/off lever to switch on and off the protective device;

7.4.2.7. Warning sign "Do not open cover until power is disconnected";

7.4.2.8. Interlocking mechanism between the quick-opening cover and the switch-on/off lever.

7.5. Repair of earth leakage protection relays for explosion-proof and leakage lockout relays must comply with the following requirements:

7.5.1. The repair results must not change the technical features as well as the explosion-proof features of the equipment.

7.5.2. After repair, the earth leakage protection relay must be tested by certification organizations.

8. Requirements and testing methods

8.1. Environmental requirements:

8.1.1. Ambient temperature from -20 °C to +40 °C;

8.1.2. Relative humidity up to (98 ± 2)% at 35 °C;

8.1.3. Oxygen content is 21% by volume;

8.1.4. No flammable gases, toxic gases, or corrosive vapors.

8.2. Testing equipment must have appropriate accuracy to measure the values of the parameters to be tested.

8.3. Testing of the parameters of the earth leakage protection relay.

8.3.1. Testing of parameters related to explosion-proof performance.

8.3.1.1. For relays designed to operate independently, they must have a non-explosive-proof enclosure type "d".

8.3.1.2. The explosion-proof enclosure is tested and inspected in accordance with the provisions of TCVN 10888-0:2015 (IEC 60079-0:2011), TCVN 10888-1:2015 (IEC 60079-1:2014), TCVN 7079-7, TCVN 7079-11.ầ8.3.2. Testing of technical parameter values.

8.3.2.1. Testing of the switch-on/off lever and interlocking mechanism.

8.1.2. Relative humidity value up to (98 ± 2) % at 35 °C;

8.1.3. Oxygen content is 21 % by volume;

8.1.4. No flammable gases, toxic gases, or corrosive vapors.

8.2. Testing equipment must have appropriate accuracy to measure the values of the parameters to be tested.

8.3. Testing the parameters of the explosion-proof leakage current protective relay.

8.3.1. Testing the parameters related to explosion-proof performance.

8.3.1.1. For relays designed to operate independently, they must have an "d" type of explosion-proof enclosure.

8.3.1.2. The explosion-proof enclosure is inspected and tested in accordance with the provisions of TCVN 10888-0:2015 (IEC 60079-0:2011), TCVN 10888-1:2015 (IEC 60079-1:2014), TCVN 7079-7, TCVN 7079-11.

8.3.2. Checking and testing technical parameters.

8.3.2.1. Checking the manual switch-on/off mechanism and interlocking mechanism.

three-phase symmetrical leakage test

8.3.2.1.1. When manually opening and closing the relay's earth fault protection must immediately cut off power.

8.3.2.1.2. The quick-opening cover can only be opened when the manual opening and closing mechanism is in the open position and the interlocking mechanism has been released.

8.3.2.1.3. Once the quick-opening cover is opened, the manual opening and closing mechanism cannot operate.

8.3.2.2. Insulation endurance testing

8.3.2.2.1. The insulation endurance of the relay is tested using high voltage, industrial frequency, for a test duration of 1 minute, with test values specified in Tables 7 and 8 of this Technical Standard. The result should not puncture the insulation or cause surface discharge on the insulation.

8.3.2.2.2. The insulation resistance of the earth fault protection relay and the earth fault lockout must be tested, with permissible values specified in Table 9 of this Technical Standard.

8.3.2.3. The reliable operation test of the earth fault protection relay is conducted at rated voltage; when pressing the "test" button, the earth fault protection relay operates and cuts off power, the earth fault lockout relay operates to prevent power from being restored, and the indicator lights must illuminate.

8.3.3.4. Three-phase symmetrical earth fault testing

8.3.3.4.1. Testing is conducted at rated voltage;

8.3.3.4.2. The test circuit diagram is modeled according to Figure 10;

8.3.3.4.3. The adjustable test resistor scale is 0.1 kΩ;

8.3.3.4.4. Testing is performed with a capacitor value of 0.22 µF and adjusting the compensation level with non-automatic compensation equipment, reducing the resistance value by 0.1 kΩ per step until the protective device activates.

Record the test results: activation resistance, leakage current corresponding to the activation resistance.

Activation resistance is the smallest value obtained from three tests.

Figure 10. Test circuit diagram for three-phase symmetrical earth fault testingng roadỏDecisionđổ Section 12.

8.3.3.5. Single-phase earth fault testing

8.3.3.5.1. Testing is conducted at rated voltage;

8.3.3.5.2. The test circuit diagram is modeled according to Figure 11;

8.3.3.5.3. The adjustable test resistor scale is 0.1 kΩ;

8.3.3.5.4. The capacitor can be adjusted to capacitance values of 0.22 µF, 0.47 µF, 0.69 µF, and 1 µF.

8.3.3.5.5. Testing is performed with four capacitor capacitance values and adjusting the compensation level with non-automatic compensation equipment, reducing the resistance value by 0.1 kΩ per step until the protective device activates.

Record the results for each capacitor value: activation resistance, leakage current corresponding to the activation resistance.

Activation resistance is the smallest value obtained from the tests.

Long-term leakage current is the largest value obtained from the tests.

Figure 11. Test circuit diagram for single-phase earth fault testing

8.3.3.6. Determining the tripping time with a single-phase earth fault resistance of 1 kΩ

8.3.3.6.1. Testing is conducted at rated operating voltage

8.3.3.6.2. Determine the tripping time of the protection when a person touches the live grid using a test resistor equivalent to human body resistance (1 kΩ).

8.3.3.6.3. The test circuit diagram for determining tripping time is modeled according to Figure 12.

8.3.3.6.4. Testing is performed with capacitor values of 0.22 µF, 0.47 µF, 0.69 µF, and 1 µF and adjusting the compensation level appropriately for non-automatic compensation type.

Record the results: tripping time, leakage current corresponding to the activation resistance.

The longest value among the ten test results under the same conditions will be taken as the specific tripping time of the earth fault relay.

Leakage current is the largest measured value.

Hìtv Sketch map of the actual site condition of the works to be received. figure 12.

8.3.3.5. Reliable operation test of the earth fault relay during voltage fluctuations

Adjust the grid voltage to the rated voltage and measure the earth fault impedance and the value of the earth fault relay impedance. Then, increase the grid voltage to 110% of the rated voltage and decrease it to 85% of the rated voltage and measure the values of the earth fault impedance and the value of the earth fault relay impedance correspondingly, must meet the requirements specified in Table 6 of this Technical Standard.

8.3.3.6. Test the operation of the earth fault relay when simulating a ground arc fault.

Use an equivalent simulation diagram with a test source having a neutral grounded with a network capacitance of 1 µF/phase, adjust the test supply voltage to 60% of the network rated voltage (simulating the voltage state during a two-phase ground arc fault), the earth fault protection device must operate within no more than 0.1 seconds in ten consecutive tests.

8.3.3.7. Check the self-test function of the earth fault protection relay:

8.3.3.7.1. The test is conducted at the rated voltage;

8.3.3.7.2. The earth fault protection relay is tested with the power supply cut off, the relay will activate to cut off the power supply.

8.3.3.8. Test the parameters of the earth fault lockout relay

8.3.3.8.1. The test is performed at the rated voltage;

8.3.3.8.2. Use a voltmeter and ammeter to determine the parameters of the earth fault lockout circuit.

8.3.3.8.2.1. The positive pole must be on the ground connection wire;

8.3.3.8.2.2. The maximum voltage must not exceed 40 Vdc;

8.3.3.8.2.3. The short-circuit current must be less than or equal to 5 mA.

8.3.3.9. Test the operating value of the earth fault lockout relay.

8.3.3.9.1. The test is conducted at the rated voltage;

8.3.3.9.2. The earth fault lockout relay operating resistance with the network capacitance being zero, by connecting the auxiliary circuit to a load with an earth fault resistance exceeding the operating resistance. Then, gradually reduce the earth fault resistance from 0.1 kΩ until the signal light turns on. The smallest value obtained from three tests is taken as the operating resistance of the earth fault lockout relay. Record the operating current value of the earth fault lockout circuit.

8.3.3.10. Test the return value of the earth fault lockout relay

8.3.3.10.1. The test is conducted at the rated working voltage;

8.3.3.10.2. The earth fault resistance at which the earth fault lockout relay returns to its initial state with the network capacitance being zero, the earth fault resistance increases in steps of 0.1 kΩ from the operating value of the earth fault lockout relay to the value at which it returns to its initial state, the return value does not exceed 150% of the operating value (Rtv ≤ 1.5 Rtđ)_{10.3.3. Certification testing must be carried out by one of the following organizations:} ≤ 1,5 R_tđ).

8.3.3.11. Test the spark safety of the earth fault lockout circuit.

The testing method is carried out according to the provisions of Article 9.1 and Article 9.2 of TCVN 7079-11:2002 (IEC 60079-11:2011).

8.2. Domestic-produced TNP1 explosive must declare compliance according to Circular No. 28/2012/TT-BKHCN dated December 12, 2012, issued by the Minister of Science and Technology regarding declaration of conformity to standards and technical regulations and methods of conformity assessment (hereinafter referred to as Circular No. 28/2012/TT-BKHCN) and Circular No. 02/2017/TT-BKHCN dated March 31, 2017, issued by the Minister of Science and Technology amending and supplementing certain provisions of Circular No. 28/2012/TT-BKHCN dated December 12, 2012, issued by the Minister of Science and Technology regarding declaration of conformity to standards and technical regulations and methods of conformity assessment (hereinafter referred to as Circular No. 02/2017/TT-BKHCN).

9. Labeling regulations

9.1. Content marked on the label

The information marked on the label of the explosion-proof earth fault protection relay used in underground mines must comply with the provisions of Decree No. 43/2017/ND-CP dated April 14, 2017 of the Government on labeling of goods, amended and supplemented by Decree No. 111/2021/ND-CP dated December 9, 2021 of the Government amending and supplementing certain articles of Decree No. 43/2017/ND-CP dated April 14, 2017 of the Government on labeling of goods and parts of the earth fault protection relay must display the following contents:

9.1.1. Type, model;

9.1.2. Rated voltage, V;

9.1.3. Rated frequency, Hz;

9.1.4. Explosion-proof protection type;

9.1.5. Enclosure protection class (IP code);

9.1.6. Explosion-proof certificate number;

9.1.7. Factory serial number;

9.1.8. Spark-safe circuit parameters (if applicable);

9.1.9. Year of manufacture;

9.1.10. Weight, kg.

9.2. Material and position of the label

The label must be made of white steel or copper with a thickness of 1.5 mm, the information in the table must be engraved with a depth of no less than 0.5 mm, must be arranged in a place that is easy to see and read, and must be securely fastened to the housing by riveting or screwing.

9.3. Electrical schematic diagram plate

The electrical schematic diagram describing the operating principle and wiring method of the earth fault protection device must be attached inside the housing wall.

10. Conformity regulations

10.1. Explosion-proof earth fault protection relays within the scope of this Standard must declare conformity in accordance with the technical safety regulations in Part II of this Technical Standard, affix the conformity mark (CR mark) before entering the market.

10.2. Imported explosion-proof earth fault protection relays must implement state registration for quality inspection of imported goods in accordance with Circular No. 36/2019/TT-BCT dated November 29, 2019 of the Ministry of Industry and Trade on management of product and commodity quality group 2 under the responsibility of the Ministry of Industry and Trade.

10.3. Declaration of conformity

10.3.1. The declaration of conformity for explosion-proof earth fault protection relays must be based on the certification results of organizations certified to operate in the field according to the provisions of Decree No. 107/2016/ND-CP dated July 1, 2016 of the Government on business activities of conformity assessment services, amended and supplemented by Decree No. 154/2018/ND-CP dated November 9, 2018 of the Government amending and supplementing, abolishing some provisions on investment and business conditions in the field of State management of the Ministry of Science and Technology and some provisions on specialized inspection (hereinafter referred to as Decree No. 107/2016/ND-CP) or recognized according to the provisions of Circular No. 27/2007/TT-BKHCN dated October 31, 2007 of the Minister of Science and Technology guiding the signing and implementation of Mutual Recognition Agreements and Mutual Recognition Arrangements on conformity assessment results (hereinafter referred to as Circular No. 27/2007/TT-BKHCN).

10.3.2. Conformity certification

Conformity certification for domestically produced and imported explosion-proof earth fault protection relays shall be carried out according to Method 5 "Typical sample testing and production process evaluation; monitoring through sampling testing at the production site or on the market or import consignment combined with production process evaluation" or Method 7 "Testing and evaluating batches of products and commodities" at the production facility according to Clause 1 of Article 5 of Circular No. 28/2012/TT-BKHCN.

≤ 2 Ω, measured at any position.

10.3.3.1. Testing for domestically produced explosion-proof earth leakage protection relays: Testing shall be conducted in accordance with the provisions of Decree No. 107/2016/ND-CP, Decree No. 154/2018/ND-CP, or testing organizations designated by the Ministry of Industry and Trade pursuant to Circular No. 36/2019/TT-BCT, or organizations recognized under Circular No. 27/2007/TT-BKHCN.

10.3.3.2. Testing for imported explosion-proof earth leakage protection relays: Testing shall be conducted by organizations designated by the Ministry of Industry and Trade pursuant to Circular No. 36/2019/TT-BCT and Decree No. 154/2018/ND-CP dated September 11, 2018 of the Government, or organizations recognized under Circular No. 27/2007/TT-BKHCN.

10.3.4. The conformity mark must comply with the provisions set forth in Clause 2, Article 4 on certification of compliance, conformity assessment, and announcement of compliance and conformity assessment issued together with Circular No. 28/2012/TT-BKHCN.

10.3.5. Procedures, formalities, and documentation for conformity announcement

Procedures, formalities, and documentation for conformity announcement for domestically produced and imported explosion-proof earth leakage protection relays shall be carried out in accordance with Circular No. 36/2019/TT-BCT dated November 29, 2019 of the Minister of Industry and Trade on quality management of products and goods under the responsibility of the Ministry of Industry and Trade.

11. Requirements for management file documentation for explosion-proof earth leakage protection relays used in underground mines

11.1. Must have complete technical documents from the manufacturer, including: User manual, maintenance, and storage instructions. In cases where technical documents are in a foreign language, they must be translated into Vietnamese.

11.2. Organizations and individuals using explosion-proof earth leakage protection relays must establish management files from the time of initial use, specifically:

11.2.1. For explosion-proof earth leakage protection relays designed for independent use in electrical networks, the following must be included:

11.2.1.1. Installation and construction methods of explosion-proof earth leakage protection relays approved.

11.2.1.2. Post-installation acceptance documents.

11.2.1.3. Calibration and testing inspection documents.

11.2.1.4. Operating procedures.

11.2.1.5. Technical safety inspection results and operational status monitoring logs for explosion-proof earth leakage protection relays used in underground mines.

11.2.1.6. Safety regulations, installation, inspection, operation, maintenance, repair, and storage procedures for explosion-proof earth leakage protection relays used in underground mines.

11.2.2. For explosion-proof earth leakage protection relays designed as blocks or integrated within other explosion-proof electrical equipment, the management files must be established according to the equipment in which the relay is integrated.

12. Requirements for inspection during operation

12.1. Explosion-proof earth leakage protection relays used in underground mines must be inspected during operation in accordance with the provisions of this Technical Standard.

12.2. Visual inspection: Inspection that does not require the use of tools or devices.

12.3. Direct inspection: Inspection of external components through visual means and determination of defects using tools and devices. Direct inspection shall not involve opening the casing or disconnecting power to the device.

12.4. Detailed inspection: Inspection that includes the contents of direct inspection and determination of defects using tools and devices. Detailed inspection requires disconnection of power and opening of the device's casing.

13. Inspection period and content

13.1. Responsibility and frequency of inspection:

13.1.1. Operators or permanent electricians shall inspect at the beginning of each shift.

13.1.2. Deputy Workshop Electrical Managers or authorized persons shall inspect weekly.

13.1.3. Electrical Department Heads or authorized persons shall inspect quarterly.

13.1.4. Deputy Electrical Directors or designated persons shall inspect annually.

13.2. Inspection content shall be carried out in accordance with the provisions of Appendix A of this Technical Standard.

13.3. Inspection results must be:

13.3.1. Recorded in the inspection log as prescribed in Appendix C of this Technical Standard.

13.3.2. Concluded regarding the technical safety condition of explosion-proof earth leakage protection relays used in underground mines, and only allowed to be put into use or continue operation when safety standards are met.

13.4. When discovering that the relay does not meet safety requirements, the observer or operator must stop the operation and report to responsible persons for handling.

14. Requirements for testing and inspection

14.1. According to the types of inspections and tests, these must be performed in accordance with technical guidance, testing methods, testing procedures, and testing equipment specified in Vietnamese Standards TCVN 4255:2008 (IEC 60529:2001), TCVN 10888-0:2015 (IEC 60079-0:2011), TCVN 10888-1:2015 (IEC 60079-1:2014), TCVN 7079-7:2002, TCVN 7079-11:2002, TCVN 7079-17:2003, IEC 60079-7:2015, IEC 60079-11:2011, IEC 60079-17:2013, and the requirements of this standard.

14.1.1. Specific items and parameters of the inspection and testing steps shall be carried out in accordance with the technical standards applied and the manufacturer's technical guidance documents.

14.1.2. Measuring instruments (voltage, current, frequency meters, insulation resistance testers, temperature, humidity, methane gas detectors) used in the inspection, testing, and calibration procedures of this Technical Standard must be calibrated, tested, and verified in accordance with legal metrology regulations.

14.2. Reporting and evaluating test and inspection results

14.2.1. Tests and inspections are considered satisfactory when: They meet the technical requirements of the applicable standards and technical standards listed in Table B of Appendix B of this Technical Standard.

14.2.2. Tests and inspections are considered unsatisfactory when: They fail to meet one of the technical requirements of the applicable standards and technical standards listed in Table B of Appendix B of this Technical Standard.

IV. RESPONSIBILITIES OF ORGANIZATIONS AND INDIVIDUALS

15. Responsibilities of organizations and individualsân

15.1. Organizations and individuals related to production, import, testing, inspection, certification, appraisal, and use of explosion-proof earth leakage protection relays in underground mines must comply with the provisions of this Technical Standard.

15.2. Organizations and individuals using explosion-proof earth leakage protection relays in underground mines must:

15.2.1. Regularly inspect explosion-proof earth leakage protection relays in accordance with regulations, promptly report and handle incidents or signs of safety issues during operation.

15.2.2. Repair, maintenance, testing, and inspection of explosion-proof earth leakage protection relays in accordance with the technical regulations set forth herein and other relevant legal documents.

15.2.3. Establish records for monitoring, managing, and safely using explosion-proof earth leakage protection relays installed in underground mines in accordance with the technical regulations set forth herein.

15.3. Testing and Inspection Organizations

Testing and inspection organizations must comply with the contents stipulated in these technical regulations and bear responsibility for the results of their tests and inspections in accordance with current regulations.

V. IMPLEMENTATION

16. Implementation Organization

16.1. The Department of Safety Technology and Industrial Environment under the Ministry of Industry and Trade shall be responsible for:

16.1.1. Providing guidance and organizing the implementation of the provisions set forth in these technical regulations.

16.1.2. Conducting inspections to ensure compliance with the provisions set forth in these technical regulations for organizations related to explosion-proof earth leakage protection devices used in underground mines.

16.2. Provincial Departments of Industry and Trade shall organize inspections to ensure compliance with the provisions set forth in these technical regulations within their jurisdictional functions and powers.

17. Effective Date

17.1. These technical regulations shall take effect from July 1, 2023.

17.2. In cases where the legal documents, standards, or technical regulations referred to in these technical regulations are amended, supplemented, or replaced, they shall be implemented in accordance with the new regulations.

17.3. Organizations and individuals implementing these technical regulations, if encountering difficulties or obstacles during implementation, are advised to report to the Ministry of Industry and Trade for consideration and resolution./.

 

ANNEX A

INSPECTION CONTENTS

I. Shift Inspection:

The shift inspection contents are specified in Table A1.

Table A1. Provisions on shift inspection contents

- Clean dust and dirt from the outer surface above the housing.

- Label plates must be complete, intact, clean, and legible without damage or fading of information, making it difficult to read clearly.

II. Weekly Inspection:

Power Circuit and Auxiliary Grounding Circuit Cable Connectors

Tighten all bolts and anti-loosening mechanisms of the cable connectors.

III. Quarterly Inspection:

IV. Annual inspection:

In addition to the quarterly inspection tasks, additional contents must be inspected according to the provisions in Table A4.

Table A4. Specifies the annual inspection contents

14.3. The inspection results must be recorded in the inspection logbook according to the approved format.

14.4. The inspection results must be processed and necessary decisions made to ensure safe machine operation.

14.5. When discovering that the earth leakage relay does not ensure personnel safety, the monitoring and operation must be stopped and reported to responsible persons for handling.

14.6. Inspection results

After inspection, conclusions about the technical safety status of the earth leakage relay used in underground mines must be drawn, and only those earth leakage relays ensuring technical safety may be put into use or continue to operate.

 

Provisions on the HS Code of Terrestrial Mobile Radio Equipment and Terrestrial Radio Relay Equipment

CONTENTS OF TESTING AND INSPECTION

I. Testing and inspection contents as specified in Table B

Table B. Specifies testing and inspection contents

 

Annex C

TECHNICAL SAFETY INSPECTION RESULTS LOGBOOK AND MONITORING OF EARTH LEAKAGE RELAY EXPLOSION-PROOF DEVICE OPERATING STATUS IN UNDERGROUND MINES

Department, Site, Workshop: …

Unit: ....

Inspection date: …

Inspector: …

Part I

Partần II

Instructions for recording, amended and supplemented by Decree No. 109/2025/NĐ-CP and Decree No. 193/2025/NĐ-CP

Part I:

Column 1: Serial number of inspection contents.

Column 2: Names of inspection contents as specified in Appendix A of this technical regulation.

Column 3: Inspection contents meeting requirements: mark “V”.

Column 4: Inspection contents not meeting requirements: mark “V”.

PART II: Record defects (details of defects, severity, and repair methods).

The person assigned to carry out inspections records the nature and severity of defects in column 2.

In column 3, the manager records detailed repair plans for defective parts and the person responsible for implementing the repair plans.

Note:

a) The person responsible for these logs must have expertise in mine electromechanics.

b) The logs must be numbered and stamped with the mine's seal.

c) Quarterly and annual inspection results must not be recorded in the log but must be documented in minutes and include all technical safety inspection parameters. The deputy director in charge of electromechanics must review and sign the minutes./.